View to view image correction for object motion with truncated data

Abstract

An apparatus for correcting patient motion between views in a medical imaging device employing multiple views in the generation of an image, and where some view data is truncated as a result of the finite area of the detector array, establishes a last row in the matrix of data for each view prior to and independent of the truncation for the purposes of evaluating motion. The data prior to this last row is compared with the data from the previous view with repeated relative shifts between the data to determine a lowest difference sum. Several difference sums may be employed to determine a shifting amount including a fractional part of a row.

I claim: 
     
       1. An apparatus for correcting patient motion occurring along an axis between views, in an imaging apparatus employing multiple views in constructing an image, the apparatus comprising: a detector for collecting a first and second view of an object, the first and second views including brightness data having values in order rows along the axis, the brightness data truncated by the detector for rows beyond a row limit;   a means for establishing a last row number common to the first and second views, before the row limit and independent of the row limit;   a comparator for comparing the brightness of the data of each row of the first view with the brightness of the data of each corresponding row of the second view only for rows before the row limit to produce a difference sum indicating the similarity of values of said brightness data between the first and second views;   a shifter for shifting the brightness data in the corresponding row of the second view by a number of rows so that the difference sum indicates the greatest similarity in the correspondingly ordered values of said brightness data between the first and second rows; and   a view corrector repositioning the second view by the number of rows to correct patient motion in the second view.   
     
     
       2. The apparatus of claim 1 including means for normalizing the brightness data of the second view to the brightness data of the first view. 
     
     
       3. The apparatus of claim 2 wherein the comparator subtracts the brightness data of each row of the first view from the brightness of the data of each corresponding row of the second view, for rows before the row limit, to produce a component difference for each row having a magnitude and sign and then sums the component differences observing both magnitudes and signs to produce the difference sum indicating the similarity of such brightness data. 
     
     
       4. The apparatus of claim 1 wherein the first and second views also include brightness data in columns perpendicular to the rows; and   including an adder for summing the column data together for each row to produce the brightness data for the first and second rows.   
     
     
       5. The apparatus of claim 4 wherein the means for establishing the last row number selects the first row between the first and second views having the greatest change in brightness from a preceding row of that view with respect to each pair of rows of that view. 
     
     
       6. The apparatus of claim 1 including additionally: a means for generating a fractional shift number based on an evaluation of the difference sums associated with the shifted second view; and   an interpolator for interpolating from the brightness data in the corresponding rows of the second view, new brightness data at a point equal to the fractional shift between the corresponding rows of the second view.